Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-05-17
2001-02-27
Kumar, Shailendra (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S134000, C564S136000, C564S137000, C564S159000, C564S160000
Reexamination Certificate
active
06194613
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for the continuous preparation of hydroxyalkylamides from carboxylic esters and hydroxyalkylamines.
2. Discussion of the Background
DE-A 25 09 237 describes a process for preparing hydroxyalkylamides. In this process, esters and hydroxyalkylamines are reacted batchwise in the presence or absence of a solvent to give the end product. The reaction takes a number of hours.
The process is improved in EP-A-O 473 380. The temperature is selected so that a crystal slurry is formed during the reaction. The partial crystallization leads to yield improvements, since the undesirable formation of dimers of the target molecule, which is associated with elimination of hydroxyalkylamine, is suppressed. Here too, the reaction is carried out batchwise. The reaction time is a number of hours.
These synthetic methods practiced hitherto have various disadvantages: if the reaction is carried out in a solvent, the solvent has to be removed again afterwards.
The customary preparation requires slow dropwise addition of the hydroxyalkylamine.
The technique of working in a crystal slurry requires accurate correlation of viscosity and temperature, since excessive crystal formation reduces the yield. In addition, the discharge of the crystal slurry from the reactor and the subsequent compounding of the material are complicated.
OBJECTS OF THE INVENTION
One object of the present invention is to provide a less complicated, simple and continuous process for preparing hydroxyalkylamides which does not have the disadvantages mentioned.
SUMMARY OF THE INVENTION
It has been found that the preparation of hydroxyalkylamides can be carried out continuously in an extruder or intensive mixer with significant benefit.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides a process for the continuous preparation of hydroxyalkylamides from carboxylic esters (or anhydrides) and alkanolamines, wherein the reaction of the starting materials is carried out in an extruder or intensive mixer by intensive mixing and brief reaction with supply of heat and simultaneous removal of the alcohol formed, and the final product is then isolated.
The process of the invention is in principle not restricted to any specific carboxylic esters and alkanolamines as starting materials.
An important principle of the invention process is that the starting materials are continuously heated briefly to a high temperature, e.g. in an intensive kneader, a singlescrew or multiscrew extruder, planetary-gear extruder, in particular a twinscrew extruder, with the corresponding alcohol being removed under reduced pressure or by stripping with gas and the intended product subsequently being isolated. The isolation is preferably carried out by subsequent rapid cooling.
It was surprising that the reaction, which requires a number of hours in the batchwise process, proceeds to a high degree of conversion in a short time. The formation of a crystal slurry of a particular viscosity, which is a difficult-to-control step in the prior art, is not necessary here. The formation of dimers can be virtually completely suppressed when the appropriate parameters are set, although high temperatures which are supposed to force dimer formation are employed at the beginning of the process.
Depending on the aim of the synthesis, it is, however, also possible to prepare products which comprise not only monomers but also additional dimers. Preparing dimers as main product is also possible.
An important aspect is the fact that brief heating in the extruder or intensive mixer at the beginning of the reaction is sufficient to react the reactants very substantially. In general, a temperature at the beginning of the reaction of at least 100° C., preferably 150° C., is required.
In a preferred embodiment of the process, the reaction is carried out in an extruder or intensive mixer having a plurality of identical or different barrel sections which can be thermally controlled independently of one another.
This is made possible by appropriate equipping of the mixing chambers or by means of the screw geometry, and also by intensive, rapid mixing with simultaneous, intensive heat exchange. This achieves uniform flow in the longitudinal direction with a very uniform residence time. Heat exchange is achieved by different temperature control in the individual barrel sections or zones of the apparatus. The temperature in the individual barrel sections is preferably 100° C.-250° C. at the beginning of the reaction and decreases from there on.
The starting materials are generally metered in in separate streams, but some of them can also be fed in together. However, it is also possible to meter in only one material stream which contains all of the starting materials. Hydroxyalkylamines or mixtures of various hydroxyalkylamines, and/or carboxylic esters and/or catalysts, and/or additives such as fluidizers and stabilizers can be combined into one starting material stream; likewise carboxylic esters, mixtures of esters and also the abovementioned additives and catalysts.
The material streams can also be divided and thus fed in in different proportions at various points on the extruder or intensive mixer. This produces targeted concentration gradients which can contribute to the completeness of the reaction.
The entry points of the starting material streams in the sequence can be varied and offset timewise.
The completeness of the reaction is ensured by removing the alcohol formed in the animation. This removal is preferably carried out by taking off the alcohols by means of reduced pressure via openings in the barrel of the extruder or intensive mixer and/or by passing a gas stream over the intensively mixed reaction mixture, in which case the more volatile alcohols are carried out by the gas stream.
The reaction can be accelerated by means of catalysts. Suitable catalysts are hydroxides and/or alkoxides of alkali metals, e.g. sodium or potassium hydroxide, sodium or potassium ethoxide, quaternary ammonium hydroxides, alkoxides and/or other strong bases. The concentration is from 0.01 to 5%, preferably from 0.1 to 1%, based on the carboxylic ester used.
Vacuum domes or gas passing-over points can be arranged in various ways and depend on the type of starting materials and on the alcohols formed. An additional point for removing residual alcohol downstream of the actual reaction section is also possible.
The preferably rapid, intensive cooling which is carried out after the rapid reaction can be integrated into the reaction section in the form of a multizone embodiment as in the case of extruders or Conterna machines. It is also possible to use: shell-and-tube heat exchangers, pipe loops, cooling rollers, air conveyors and metal conveyor belts.
Depending on its viscosity, the final product is first brought to a suitable temperature by further cooling by means of appropriate, abovementioned apparatuses and is then pelletized or comminuted to a desired particle size by means of crushing rolls, a pin mill, a hammer mill, flaking rolls or the like.
A preferred embodiment of the invention is a process for the continuous preparation of hydroxyalkylamides of the formula 1 from carboxylic esters and alkanolamines
where the substituents have the following meanings:
X: a bond, hydrogen when m=0, an alkyl, aryl, alkenyl, alkoxycarbonyl or carboxyalkenyl radical having 1-24 carbon atoms or these heteroatom-substituted radicals;
R
1
: hydrogen, an alkyl, alkenyl, aryl or aralkyl radical having 1-24 carbon atoms, these heteroatom-substituted radicals or
R
2
: independently of one another, identical or different radicals selected from the group consisting of hydrogen, alkyl, aryl, aralkyl and alkenyl radicals having 1-24 carbon atoms and these heteroatom-substituted radicals; n: integer from 1 to 10;
m: integer from 0 to 2.
The process is particularly suitable for preparing
REFERENCES:
patent: 4615831 (1986-10-01), Kanno et al.
patent: 5101073 (1992-03-01), Schlaefer
Behrendt Klaus
Elm Rainer
Herda Silvia
Weihrauch Thomas
Creanova Spezialchemie GmbH
Kumar Shailendra
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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